Process of producing transparent and waterproof paper



Patented Nov. 16, 1926;

PATENT OFFIC v AUGUSTUS E. MAZE, OF ORANGE, NEW JERSEY, ASSIGNOR '10 ELLIS-FOSTER COMPANY,

OF MONTCLAIR, NEW JERSEY.

PROCESS OF PRODUCING TRANSPARENT .AN'ID WATERPROOF PAPER.

No Drawing.

Transparent or translucent paper ordinarily is produced either by treatment resulting 111 a modification of the fibres composing the paper, or by the incorporation ofa' material with the fibres, which results in the production of a translucent, or fairly trans parent sheet. My invention applies to the production of transparent or translucent and waterproofed paper, especially thin paper, by the incorporation of certain materials, which fill the interstices and afford the transparent or translucent and waterproofing efi'ects desired. The present practice is that of preparing a sheet of paper, immers- ,ing it in a bath of molten wax, oil or resin. In carrylng out my invention I prepare an emulsion of the wax, oil, resin, or mixtures thereof, employing Water. as the vehirole, and preferably using a colloid mill to convert the waterproofing agent into a state of extreme fineness or dispersion. It is advantageous, but not essentially necessary to previously dissolve in the water 'a small amount of a soluble soap, such as sodium or potassium stearate, palmitate, resinate and the like. In other cases a small amount of an alkaline salt such as sodium phosphate, soda ash, or of an alkali such as caustic soda or potash may be employed in lieu of the soap.

Having prepared the emulsion by means of a powerful emulsifying means such as the aforesaid colloid mill, I introduce said emulsion into the beater with the pulp. I find it highly desirable to add the emulsion after the pulp has been thoroughly disintegrated and hydrated, and is ready to be removed from the beater. The emulsion is rapidly absorbed by the fibres (the speed of absorption depending to some extent on the proportion of hydrocellulose present) and the sheet is then formed inthe usual manner. On drying the paper the emulsified material is left occluded in and upon the fibres. On passing the sheet through calender rolls, the latter preferably hot, the occluded'material is forced'under high pressure even more thoroughly throughout the sheet and such uniform distribution renders sheets of thin paper unusually transparent Application filed December 30, 1925. Serial No. 78,329.

is being fed onto the screen on which the sheet is being formed. The emulsion is rapidly absorbed by the fibres and on drying colloidal bonding takes place in a notable manner. The paper made in this manner is finally calendered. It should be noted that paper Which has been well-worked in the beater contains a certain amount of 11ydrocellulose in dispersed form and this colloidal agent coming in contact with the dispersion of the substantially homogenized wax or'other waterproofing agent, through certain adsorptive phenomena, causes its occlusive union with a part of the fibre. The action is quite a different one from that which occurs when a sheet of paper is passed through a bath of, for example, molten paraflin.- Under these conditions there is no colloidal occlusion. In accordance with my invention, colloidal occlusion, I believe, constitutes a very important mechanism, lending qualities of translucency or transparency which is particularly desirable.

To enhance -the effect it 'is therefore desirable to subject the paper pulp to treatment in the beater over a longer period than is usually customary, as thereby I develop hydrocellulose, or. fibres having a surface coating of hydrocellulose, which acts to give the occlusive effects which I deem of importance herein.

A third method which may be employed in some cases, is to form the sheet, especially paper stock which contains some hydrocellulose, and before the sheet is entirely dry, that. is, while the colloid character of the fibres or their coatings is still in evidence, I spray the emulsion upon the sheet. The emulsion penetrates more rapidly when a relatively large quantity of Water is prescut in the sheet than when drying has progressed to a considerable degree. I may employ suction to aid in the penetration of the emulsion, but do not find it generally necessary. Still another modification consists in passing the sheet after formation and before it is entirely dry into and through the emulsion. In this case also the emulsion penetrates more rapidly when the sheet contains a relatively large proportion of moisture.

As an illustrative example dissolve 4 lbs. of sodium stearate in 12 gals. ofwater, the latter preferably hot. This solution is heated to a temperature somewhat above the melting point of the Wax or wax resin and. the like employed. Preferably I use paraflin Wax and heat the soap solution to about 90 (1, adding thereto 100 lbs. of the wax. At a temperature of 90 C. I introduce the mixture of melted wax and stearate solution into a colloid mill, thereby bringing about a high degree of emulsification, and in some cases, what may be termed homogenization. Approximately 200 lbs. of emulsion is obtained which is suflicient to treat about 700 lbs. of paper or paper pulp.

Paratlin wax, especially the harder varieties of the wax, which I prefer, is difficult in the form of an emulsion, to incorporate with dry paper, or paper stock, to secure a blending of a satisfactory character. There exists an incompataloility, which I find to dis appear when the wax is substantially homogenized by the colloid mill and is incorporated with paper fibre having a coating of hydrocellulose. The occlusion of the wax under these conditions of ultra-colloidal absorption, bonds paper fibre and wax together i in a manner, which apparently is retained on drying and calendering and yields the novel product of the present invention.

It should be noted that the emulsion is noninflammable which is advantageous in contrast to methods of impregnating wax employing solutions of the latter and light petroleum solvents, benzol, and the like.

The process therefore in its preferred form for producing a transparent or translucent and Waterproofed paper comprises forming an emulsion of paraffin wax, in which the latter is so completely and effectively dispersed as to be substantially homogenized and incorporating such dispersion with paper pulp, either in mass or in sheeted form, which is wet, or contains a substantial amount of moisture, the fibres of which paper stock have been subjected to mechanical agitation or beating sufficient to develop the formation of hydrocellulose to some extent, whereby I obtain a. powerful occlusive and uniting effect.

The invention further comprises the product of such process, e. g, a sheet of paper containing such colloidally-welded wax or analogous waterproofing agent. While I have mentioned resins and other bodies, I prefer in most cases, to employ paraflin wax, as thereby it is possible to secure a paper product which is light in color and is effectively waterproofed. By the ,process of the present invention I am able to prepare papers of notable transparency with the employment of a minimum amount of wax and thereby the cost of manufacture of such products in comparison with other methods heretofore used is decreased. In addition to paraffin wax certain other waxes may be employed, or, in some cases, in order to raise the melting point of the paraffin wax, a hard wax such as carnauba wax may be admixed with it.

To secure the best results in accordance with the preferred form of my lnventlon I find it desirable to employ as the paper stock sulphite pulp or other pulp which has never been thoroughly dried. The wet pulp as it is obtained from the pulp mills represents a cheap and convenient source of the raw material. Pulp of this character, or any other suitable stock, is treated in the beater engine for a period of several hours, usually not less than live or ten hours, and preferably for a somewhat longer period, at times for a duration of thirty hours, or so. In this operation it is desirable to use in the beater engine blades which are rather blunt and'are set with as little clearance as possible to obtain a maximum degree of crushing and beating effect whereby hydrated cellulose is advantageously formed. The exact duration of the treatment in the beater engine or hollander is not a fixed one, but depends upon the degree of hydration desired. If stock is to be made which will yield paper of the quality well known to the paper trade as Glassine, the treatment in the beater should be continued until the pulp assumes a slippery mucilaginous feel, somewhat resembling that of moist agar agar." Pulp carried to this stage of hydration yields of itself, when made into thin sheets, a transparent to translucent product, which, however, is not resistant to water. Pulp of this description is particularly reactive with homogenized parafiin wax and almost immediately unites with it, either by chemical action or colloidal affinity. In any event, on adding an aqueous dispersion of paraflin to well-hydrated cellulose pulp, the filtrate from the mass is practically clear, even though filtration be effected almost immediately after mixing. I do not wish to limit myself to any particular stage of hydration of the cellulose in carrying out my invention, as indicated, the preferred form contemplates a substantial degree of hydration, suflicient to engender a notable affinity towards the emulsions and dispersion involved herein. Furthermore, mixtures of hydrated cellulose and unhydrated cellulose, may be employed in preparing the paper stock, For example, dry pulp which has been thoroughly dried, or dry paper stock from any other source, which is relatively diflicult of hydration in the beater engine, may be admixed with fresh wet pulp which has never been dried and which hydrates readily, and the mixture of these two types of paper stock duly subjected to treatment in the beater.

Furthermore, in the matter of adding the emulsion or dispersion to the paper stock, I do not wish to be limited to incorporation at any particular stage. I have recommended in the foregoing that the addition of the such pulp the homogenized paraffin afore said, transparent effects of a remarkably high order are cheaply obtained with accompanying waterproofing eifects of great commercial value.

What I claim. is

1. The process of producing transparent or translucent and waterproof paper, which comprises subjectin paper pulp to a beating operation whereby ydroc-ellulose is formed in some degree, and in incorporating with the resulting, fibre whilestill moist an emulsion of substantially homogenized paraffin wax.

2. The process of producing transparent or translucent and waterproof paper which comprises subjecting paper ulp to a beating operation whereby hydroce lulose is formed in some degree, incorporating with the resulting fibre while still moist an emulsion of substantially homogenized paraflin wax, drying and calendaring the product as a sheeted material whereby a colloidally-welded Wax paper product results.

3. The process of producing Waterproof paper, which comprises treating paper pulp containing hydrocellulose, with an emulsion containing parafiin Wax, allowing the dispersed wax to react with said hydrocellulose and thereafter forming the pulp into sheet form.

4. A transparent or translucent waterproofed paper comprising a sheet of fibrous material carrying colloidallyfvelded paraflin wax.

AUGUSTUS E. aze, 

